Phelps set for farewell as Bolt, Blake take to track

American swimming icon Michael Phelps will bring the curtain down on his glittering Olympic career Saturday as attention turns to track and field and the most eagerly anticipated 100m in history. After a slow start to his campaign, Phelps could well sign off with his fourth gold medal of the Games as he aims to consolidate his position as the most decorated Olympian in history. A nail-biting victory in the men's 100m butterfly on Friday saw Phelps claim his second individual title of the Olympics after earlier bagging gold in the 4x200m freestyle relay. The 27-year-old -- who claimed a record eight golds in Beijing four years ago -- will be strongly fancied to collect the 18th gold of his career, and his 22nd career Olympic medal, in Saturday's 4x100m medley relay. In other highlights of the final day of action in the pool, China's Sun Yang will attempt to complete a long distance double by adding the 1,500m crown to the 400m crown won earlier in the games. Day two of the track and field competition will see five gold medals on offer, with British golden girl Jessica Ennis bidding to provide the host nation with a fairytale victory in the heptathlon. Ennis topped the field after the first four events on Friday, earning 4,158 points to lead Lithuania's Austra Skujyte and Canada's Jessica Zelinka, but will be anything but complacent as she heads into her final day. "I'm going to have to have a really strong day and make sure everything is really solid. There's a lot more work," Ennis said late Friday. While six athletics medals will be decided on Saturday, all eyes will be on the opening rounds of the men's 100m. Defending champion Usain Bolt and Jamaican teammates Yohan Blake and Asafa Powell will make their entrance alongside US rivals Tyson Gay and Justin Gatlin, with the semi-finals and final scheduled for Sunday. The 100m remains the premier track and field event, and arguably of the whole Olympics, with the London final being hyped as potentially the fastest ever run. "Everyone's been waiting for this for four years. It's going to live up to expectations," said Blake, who edged Bolt in the Jamaican trials and has been tipped as a genuine title contender. The women's 100m gold will also be decided following Friday's opening heats and a semi-final early in Saturday's evening session. In the women's pole vault, double Olympic champion Yelena Isinbayeva will bid to safely negotiate qualifying for Monday's final. Britain's cyclists will meanwhile attempt to extend their crushing dominance in the Velodrome, where the hosts have so far won three out of four golds on offer and are on course to match their Beijing haul of seven. The British team will expect to bag another gold in the women's team pursuit after a world-record breaking performance to reach the final. Elsewhere, the first medals of the tennis tournament at Wimbledon will be decided with Serena Williams and Maria Sharapova hunting a first Olympic singles gold medal. In the men's football tournament, Britain will attempt to reach the last four with victory against South Korea, where they will meet the winners of Brazil's quarter-final against Honduras.